1. Field of the Invention
The present invention relates to a toner supplier apparatus for supplying a liquid toner to a developer apparatus of a wet type electronic photograph printer using liquid toner.
2. Description of the Related Art
Maintaining the concentration of toner within a fixed range is extremely important in a wet-type electronic photograph printer using liquid toner (hereinafter simply called toner) since the concentration of a printed image depends on the concentration of the toner. A solution proposed in view of this situation is a toner-adjusting apparatus for adjusting the concentration of toner for image development (see for example, Patent Document 1)
The Patent Document 1 discloses a toner-adjusting apparatus including: a toner reservoir for adjusting the concentration of a toner (a back-up toner reservoir described in the Patent Document 1); a diluent-supplier section for supplying diluent to the toner reservoir; and a high-concentration-toner-supplier section for supplying a high concentration toner to the toner reservoir. In this configuration, the concentration-controlled toner is fed from the toner reservoir to a toner chamber (a toner reservoir 37B as shown in FIG. 2 of the Patent Document 1) for supplying the toner onto the developing roll. In addition, a toner-feedback pipeway extending from the toner chamber is connected to the toner reservoir so that the toner fed back to the toner reservoir is circulated and supplied to the toner chamber.
The concentration of the reserved toner, while being supplied from the toner chamber via the developing roll onto the photosensitive drum making contact with the developing roll, varies since consumption rates of the diluent and toner grains vary based on the size, density, and concentration of a printed image.
To address this situation, the toner-adjusting apparatus in an attempt to stabilize the concentration of the toner reserved in the toner chamber controls the concentration of the toner reserved in the toner reservoir within a fixed range while liquids are supplied from the diluent-supplier section and the high-concentration-toner-supplier section to the toner reservoir and while the liquid is supplied from the toner reservoir to a toner chamber in the vicinity of the developing roll. In addition, the surface level of the liquid reserved in the toner reservoir is maintained within a fixed range by such liquid flow control.
Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 2004-117687
However, the toner-adjusting apparatus described in the aforementioned Patent Document 1 has the following disadvantages (a) to (c).    (a) A concentration sensor is provided in a bottom section of the toner reservoir for controlling the concentration of the toner reserved in the toner reservoir. However, accuracy may be lowered for controlling the toner concentration since the concentration of the toner measured by the concentration sensor is vulnerable to the toner dispersed in the toner reservoir. For example, when the toner is not dispersed in the toner reservoir uniformly, particularly in a case immediately after stirring the toner, a concentration of the toner reserved in the toner reservoir and measured by the concentration sensor may differ from the concentration of the toner reserved in the toner chamber in the vicinity of the developer apparatus.    (b) There is a time-lag until the concentration of the toner reserved in the toner chamber of the developer apparatus reaches to the concentration of the toner reserved in the toner reservoir via toner-supplying pipeways and valves.    (c) The measured concentration tends to include an error because the concentration sensor of the aforementioned type measuring an attenuation rate of an ultrasonic wave transmitting in the liquid toner do not consider the temperature characteristics of a transmitter/receiver section thereof. For example, the temperature of the toner increases based on friction at a roller nip causes the transmitter section to emit a more significant signal than the true temperature, and accordingly causes the receiver section to receive a more significant level of the signal, thereby resulting a lower concentration being obtained than the true concentration.